1. Field of the Invention
This invention relates to wire and cable. In one aspect the invention relates to a strength member of a wire or cable while in another aspect, the invention relates to a strength member that is fiber reinforced. In yet another aspect the invention relates to a process for making a fiber reinforced strength member while still in another aspect, the invention relates to wire and cable comprising a fiber reinforced strength member.
2. Description of the Related Art
Fiber-optic cable is a complex structure designed to provide sufficient protection for the fibers from detrimental levels of longitudinal and transverse stresses. In addition, the structure also provides a benign chemical and physical environment for the service life of the fibers. One fundamental difference between fiber-optic cable and electrical power cable is that the metal conductors in a power cable carry at least portion of the tensile stresses created during installation and in-service conditions. In contrast, fiber-optic cables contain tensile strength members integrated into the cable specifically to isolate the fibers from tensile stresses. Sufficient tensile and compressive strength, ability to withstand small radius bend, easy fiber handling and cable installation, and competitive cost are a few criteria among the list that must be considered when designing a fiber-optic cable.
Many types of designs are available for fiber-optic cables, the design of choice dependent upon the application. Whatever the choice, all require some type of strength members to carry the tensile and compressive stresses of the cable during both installation and in-service use.
The strength members in use today are made mainly of fiber reinforced plastic (FRP, which is also known as glass reinforced plastic (GRP) if glass fiber is the reinforcement) or stainless steel. Traditionally, FRP or GRP is manufactured through a fiber pultrusion process with one or more thermoset resins such as vinyl ester or epoxy, but the speed of process is very limited. As for stainless steel, it is relatively expensive and heavy. In addition, the GRP or FRP/thermoset resin composites available today tend to have excessive stiffness, and this makes installation of fiber optic cable comprising these strength members difficult, especially around buildings or along busy city streets where sharp bending of the cable is often necessary.